Cory Gardner

Inquiries into last month's spill of toxic wastewater into the Animas River in Southwestern Colorado continue on Capitol Hill.

The Senate Environment and Public Works Committee held a hearing Wednesday into the spill at the request of lawmakers from Colorado and New Mexico.

Colorado has largely been spared from this summer's political wrangling ahead of the 2016 presidential race. But as Republicans nationally are working to narrow the presidential field, the GOP in Colorado wants to widen its field of candidates to run against incumbent Democratic Senator Michael Bennet next year.

"The numbers tell us Senator Bennet is vulnerable," said Republican state party Chairman Steve House. "It would be great to hold onto the U.S. Senate. Republicans have to defend a number of seats more than the Democrats."

With Colorado's U.S. Senate race too close to call, both parties are on an all-out blitz to court as many voters as they can prior to the November election. The youth vote has traditionally helped Democrats, but Republicans see an opening with national support for President Obama falling among the millennial generation.

Democratic Senator Mark Udall and Republican Congressman Cory Gardner had a spirited debate Tuesday night hosted by The Denver Post. Both candidates are locked in a tight race and both stayed on message in the hour-long debate.

Udall attacked Gardner as extreme and out of touch, Gardner criticized Udall for being in lockstep with President Barack Obama.

Colorado's U.S. Senate race is a considered by many to be a tossup. Incumbent Senator Mark Udall and Republican Congressman Cory Gardner are trying to win over as many key voting blocs as they can before Election Day – and that includes women.

In the previous close Senate contest between appointed Democratic Senator Michael Bennet and Republican Ken Buck, women played a critical role. During the waning days of that 2010 race, Bennet focused his attention on the female vote – and narrowly won. With women making up 51.4 percent of all registered voters in Colorado this election, it's a scenario Democrats are hoping to repeat.

A new poll released today from Quinnipiac University shows Democratic Senate incumbent Mark Udall 8 points behind his Republican challenger Congressman Cory Gardner. Bente Birkeland has more from the state capitol.

Colorado voters will once again decide on an amendment that would give unborn babies the same constitutional and legal rights as a person. The measure is bringing out some familiar faces – it’s also impacting one of the closest U.S. Senate races in the country.